Bit twiddling for checking whether a number is in particular range

Question

I found some interesting bit twiddling in \"source\\common\\unicode\\utf.h\" file of ICU library (International Components for Unicode). The bit twiddling is intend

Answer 1

The formula works whenever the range you are looking for starts at a multiple of a power of 2 (that is, 1 or more bits at the low end of the binary form of the number ends in 0) and the size of the range is 2^n-1 (that is, low&high == low and low|high == high).